code: def _to_feature_list(*spec_dicts):
      feature_list = []
      for spec_dict in spec_dicts:
          feature_list.append(dict(layer=spec_dict))
      return {"feature-list": feature_list}
  
file_path: lets-plot/python-package/test/plot/test_marginal_layer.py
imports: import pytest
  import lets_plot
label_desc: Use image node_id 5 for calling a global function with example usage: _to_feature_list() and returns: dict